An electrolytic copper plated film has been hitherto deposited and grown in a via hole (contact hole) or through hole (hereinafter referred to simply as “hole”) formed in a high-density mounting board, a semiconductor substrate or a semiconductor packaging board thereby forming a via electrode (contact electrode) or a through-hole electrode including the electrolytic copper plated film.
In order to improve the physical properties and deposition properties of the plated film, additives having promotion action and inhibition action are added to the electrolytic copper plating solution.
As a promoter having the promotion action or a promotion effect (promotion function), SPS (bis(sodium sulfopropyl)disulfide) is used, for example.
Of additives showing the inhibition action or an inhibition effect, an additive having a strong inhibition action or strong inhibition effect and having a great influence on the formation of copper plating in a via hole is called an inhibitor, and an additive having a small inhibition action or small inhibition effect and capable of improving the smoothness of a copper plated surface is called a leveler.
The inhibitor used includes, for example, PEG (poly(ethylene glycol)).
The leveler used includes, for example, a polyamine.
To stabilize the quality of a plated film, importance is placed on the control and adjustment of the amounts of additives (concentrations of promoter, inhibitor and leveler) contained in the electrolytic copper plating solution. However, as time passes from a plating reaction initiation point, the additives undergo decomposition or property changes, and the control therefor is necessary.
For the control of additives, the usual practice is to use a CVS (Cyclic Voltammetry Stripping) method. With the CVS method, the potential of a platinum rotating disk electrode is repeatedly changed in a plating solution at a given speed, so that the deposition and dissolution of a metal plated film are caused to repeatedly occur on the electrode surface.
In the CVS method, the potential scanning speed is constant, so that the dissolution of the peak area of the voltammogram is proportional to an average deposition rate, which is in close relation with the concentration of an additive in a plating solution.
If the calibration curve of a standard plating solution is made, the CVS method enables the quantitative analysis of additives in a sample plating solution to be carried out.
With an existing CVS device using the CVS method, if additives undergo degradation due to the decomposition and property changes of the additives in an electrolytic copper plating solution although depending on the elapsed time from a plating reaction initiation point, then the analysis is made in terms of the concentrations of the additives including the quantities of the degraded additives.
As an analysis method wherein such additive degradation (i.e. decomposition and property changes of additives in the electrolytic copper plating solution) are taken into account, the technique described in PTL 1 is known.
In PTL 1, it is disclosed that the analysis of MPSA (3-mercaptopropylsulfonic acid), which is a decomposed matter of SPS added as a promoter, is made by use of the CVS method.
PTL 2 discloses the analysis of the decomposed matter of a leveler component by use of a voltammetric method.
However, although the analysis methods disclosed in PTLs 1 and 2 are feasible by the use of existing CVS devices, complicated operations are needed. More particularly, such operations are necessary to check potential variations by repeating potential scanning several times, or to measure two types of plating solutions provided at different dilution rates.
As a method of analyzing the influence of decomposed matters of additives contained in an electrolytic copper plating solution according to a method simpler than the methods of PTLs 1 and 2, techniques described in PTLs 3 and 4 are known.
In PTL 3, an analysis method of determining amounts of additives is disclosed by performing constant current electrolysis on an electrolytic copper plating solution containing a gloss agent and a leveler as additives to obtain a time-potential curve.
In PTL 4, an analysis method is disclosed wherein constant current electrolysis is performed on an electrolytic copper plating solution containing additives, and the state of the electrolytic copper plating solution is judged from the resulting time-potential curve.
In the case where the analysis methods of PTLs 3 and 4 are carried out, a rotating electrode is used.